1. Field of the Invention
This invention relates to a device and method for repairing damaged laminated glass such as the safety glass utilized for the windshields of motor vehicles.
2. Description of the Related Art
Virtually every driver is familiar with the damage caused to windshields by flying rocks. The resultant fractures in the glass can be classified within four categories: bull's-eye, star, combination (of bull's-eye and star), and radial. The plastic layer inserted between the outer and inner layers of the laminated glass usually assures that any of these fractures are confined to the outer layer of glass. In the bull's-eye break, a cone of glass with its apex at the point of impact separates from the outer layer of glass with its flat end generally remaining attached to the plastic. A star break is composed of multiple cracks, each of which begins at the point of impact and travels outward therefrom. Quite logically, the combination break incorporates the features of both the bull's-eye and the star fractures. And a radial crack is a single crack which passes through the point of impact.
Various inventions have been patented to repair these fractures by replacing the air which has entered the interstices that form the fracture with a liquid resin which bonds to the glass and cures to a solid form with an index of refraction that is near to that of the glass.
All of the inventions incorporate a device for holding resin in the vicinity of the fracture and a structure for attaching this device to the glass. Most have the ability to create a vacuum above the fracture to facilitate the removal of air therefrom and the replacement of the air with resin. And some, which are designed primarily to repair bull's-eye breaks, possess a pointed probe that is used to manipulate the apex of the cone of glass in order to assist the movement of resin into the fracture.
U.S. Pat. No. 3,841,932 of C. Richard Forler and Conrad F. Heins uses pliable, moldable material to form a reservoir on a windshield into which a polymerizable resin is introduced so that it can flow into the highest point of the crack. A pointed probe is then manually used to manipulate the cone of glass. After the resin has hardened, the excess resin is sheared away.
Three inventions utilize an external source to create a vacuum above the fracture.
In U.S. Pat. No. 4,165,397 of P. H. Ogden and H. Pennicott, a vacuum cup is held on the glass by air pressure. Within the vacuum cup a reservoir is adhesively attached to the glass. Through an injectable portion of the vacuum cup, resin is injected into the reservoir while the vacuum is maintained. Then the vacuum cup is removed, and the resin penetrates the fracture and is cured. Subsequently, the reservoir is taken away; and excess resin is scraped from the glass.
A vacuum cup is also held on the glass by air pressure in U.S. Pat. No. 4,047,863 of Douglas McCluskey and Harley E. Kelchner. A vacuum is applied to the glass and subsequently removed. Next, a reservoir is formed on the glass from modeling clay, putty, or the like; the reservoir is filled with a polymerizable liquid; the vacuum cup is reinstalled; a vacuum is cyclically reinstituted; and a pointed probe manipulates the glass cone to facilitate the escape of air from the fracture. Optionally, a sleeve and plunger can be inserted into the polymerizable liquid so that the sleeve surrounds the crack and creates an area where depression of the plunger forces the liquid under pressure into the fracture. The vacuum cup is subsequently removed; the liquid, cured with ultraviolet light; and the excess material, cut away.
Finally, the invention in U.S. Pat. No. 4,280,861 of Herbert S. Schwartz has a vacuum cup which is held on the glass by air pressure. A threaded tube is screwed into the vacuum cup until the open, inner end of the tube touches the glass. The outward end of the tube is covered with a resilient disk. This disk is punctured by the needle of a syringe which injects resin into the tube and can also be used as a pointed probe to manipulate the cone of glass. An external pump and air compressor are connected to a third opening of the tube to create alternating pressure and vacuum within the tube, thereby withdrawing air from the fracture and forcing resin into it. The tube and vacuum cup are then withdrawn, the resin hardens, and excess resin is cut away.
U.S. Pat. No. 3,562,366 of William E. Sohl has two distinct embodiments. Both have in common a device which is attached to the inside of a windshield to create supersonic vibrations that assist resin to fill a fracture in the outer layer of the windshield. The embodiments differ in the structure that is used to apply resin. The first is simply a resilient cup the open end of which can be pressed onto the damaged side of the windshield; after such attachment, the cup is filled with resin through a small aperture. The cup contains either a removable or permanently attached rigid, pointed probe that presses against the cone of glass. The second version consists of a block with a chamber to hold resin that extends to, and, consequently, creates an open end of, the block; a channel leading through the block to the chamber; a syringe which can be removably inserted into the outer end of the channel; and a threaded, pointed probe that can be screwed into a threaded portion of the block, through the chamber, and against the cone of glass. The syringe forces resin into the chamber and thence into the fracture. Either embodiment of the structure for applying resin can be held against the windshield by spring-loaded frames supported from suction caps applied to the damaged outer side of the windshield.
The invention in U.S. Pat. No. 3,765,975 of Gordon P. Hollingsworth is very similar to the second embodiment of U.S. Pat. No. 3,562,366. There is a block containing a chamber to hold resin that reaches, and, therefore, establishes, an open end of the block. The needle of a syringe extends from outside the block into the chamber. The body of the syringe may be removably connected to the needle. The block is also fitted with a threaded, pointed probe which extends into the chamber. To start the repair, the block is most conveniently held on the glass by a supporting frame attached to the windshield with rubber suction cups. To start the repair, the syringe is filled with a liquid polymerizable resin and attached to the needle embedded in the block. Optionally, an initial sequence of negative and positive pressure in the chamber may then be created by retracting and extending the plunger of the syringe. This permits air to escape from the fracture and resin to flow into the chamber. The probe is next forced against the cone of glass until the cone moves. Positive and negative pressure is subsequently applied with the syringe. The apparatus is then removed; the resin, cured; and excess resin, scraped or filed away.
Two significantly different embodiments are again presented in U.S. Pat. No. 3,993,520 of Frank D. Werner and Robert W. Wiele. In the first, an injector tube having a resilient annular tip and a resilient interior is mechanically pressed, by a support structure attached to the glass with suction cups, against the damaged windshield. Resin is placed into the injector tube and forced, with a plunger that passes along the resilient interior, into the fracture in the windshield. A subsequent slight withdrawal of the plunger creates a vacuum which draws air, through the resin, from the fracture. This cycle of pressure and vacuum can be repeated as desired. The second embodiment comprises placing resin on the windshield; putting a ring of vacuum cup lubricant around the fracture; covering all the preceding with a sheet of polyethylene; placing a suction cup over the polyethylene; depressing the suction cup to force resin into the fracture, although some resin enters the fracture because of surface tension even if the suction cup is not depressed; then creating a vacuum with the suction cup; and finally, releasing the vacuum. The cycle of pressure and vacuum can, again, be repeated as desired.
In U.S. Pat. No. 4,753,695 of George E. Alexander, Von L. Alexander, and Thomas R. Spoo, the invention has an adapter that is adhesively attached to a damaged windshield. The adapter is deformable and removably receives a syringe which has been filled with a liquid polymerizable resin. The syringe can communicate with the fracture through a circular recess which extends through the adapter. It is disclosed, but not claimed, that the plunger of the syringe is first retracted a short distance to evacuate air from the fracture. Then the plunger is depressed to force resin into the fracture. After the resin has polymerized, the syringe, adapter, and any excess resin are removed.
Similarly, the invention in U.S. Pat. No. 4,200,478 of Gerald Jacino and Anthony Jacino utilizes a pedestal which is adhesively attached to a piece of damaged glass. Resin is again placed in a syringe that is then removably mounted on the pedestal, which has a chamber that extends from the syringe to the glass. A valve can connect the interior of the syringe to the atmosphere so that opening the valve before the plunger is depressed, initially to move resin from the syringe to the fracture, and closing it prior to withdrawal of the plunger creates a vacuum which removes air from the fracture and allows resin to flow into it. When, this process has been repeated a number of times, the valve is opened before the plunger is withdrawn and closed before it is again depressed, creating increased pressure to force the resin into the fracture. When the pedestal has been removed and the resin cured, excess resin may be cut away.
U.S. Pat. No. 4,840,551 of Kurt Lay and Erwin Sailer concerns an apparatus for repairing windshields; U.S. Pat. No. 4,851,169 of the same inventors claims a process that utilizes the apparatus from the earlier patent. A suction cup is placed over the damaged portion of a windshield and remains in that position by a vacuum created either with an external pump or through the tendency of the cup to regain its original shape after having been forced downward to the windshield, having expelled the air which was previously between it and the windshield, and having subsequently formed with the glass an impermeable seal around its perimeter, i.e., functioning in the well-known manner of a suction cup. Because the cup is transparent and penetrable with the needle of a syringe filled with resin, the needle can have its tip placed in the center of the fracture, where the resin is ejected from the syringe. The resin then enters the fracture because of capillary forces and the vacuum. No pressure need be exerted on the resin, nor is alternating between a vacuum and increased pressure required.
Of the devices which utilize a vacuum or the cyclical application of pressure and a vacuum, those of U.S. Pat. No. 3,993,520 and U.S. Pat. No. 4,840,551 employing a suction cup appear to be the simplest. Still, considerable skill would seem to be necessary in order to retain the resin by means of the ring of vacuum cup lubricant and the sheet of polyethylene from the former patent; and some practiced dexterity would be required to manipulate the syringe from the latter patent accurately and safely.